1. Field of the Invention
The present invention relates to transmission of mechanical power, and more particularly to transmission of mechanical power where a relatively constant output rate is desirable, such as in aircraft electrical power systems, for example.
2. Description of Related Art
A variety of devices can convert a variable mechanical input to a relatively constant rate for use in generating power at a relatively constant frequency. For example, in two stage gas turbine engines, aircraft electrical power can be produced by a generator powered by rotation of the high pressure spool. Generally, the high pressure spool has a more constant operational frequency than the low pressure spool. Even so, it is common to use a constant speed drive (CSD), or other continuously variable transmission, to regulate between the variable speed of the high pressure spool and the generator in order to keep the input to the generator more constant.
Aircraft are requiring more and more electrical power, and the amount of power that can be derived from typical high pressure spools is limited. Conventional constant speed drives and the like are also limited in that they can provide a constant output only if the input remains within a certain range. In some applications, variable frequency electrical systems can operate using variable inputs. But these also need the input to remain within a limited range.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for systems and methods for supplying power that allow for improved range of input while still providing a relatively constant output. There also remains a need in the art for such systems and methods that are easy to make and use. The present invention provides a solution for these problems.